PMR systems have been developed to meet the growing demand for improved magnetic disk drive data rate and capacity. With the ever increasing need for higher recording areal densities (over 920 GB/in2) and track densities (over 500K tracks per inch), improved processes for manufacturing PMR writers with wrap around shields (WAS) continue to be developed.
Damascene processes may be used to build up structures for use in a PMR writer head, as opposed to methods which rely upon material removal to form such structures. As applied to the formation of PMR writing heads, the damascene process involves forming trapezoidal trenches in a material, and then depositing (e.g., electroplating) a magnetic pole material into the trenches to form write poles. The PMR writer pole is the trapezoidal formation of the magnetic material deposited in the trapezoidal trench etched in a surrounding material.
An important consideration during the manufacture of PMR writers is the sidewall angle of the structure, which affects both on track performance and neighboring track impact from the head skew angle. In current magnetic disk drives, the head generally has a skew angle relative to the track direction when the head operates at inner and outer radii of the recording medium surface. This skew may cause magnetic fields from the writer pole surface to erase data in neighboring tracks. A high sidewall angle for a writer pole at an air bearing surface (ABS) prevents this skew impact on neighboring tracks. However, a high sidewall angle may also cause on track reverse overwrite loss. Optimization of the sidewall angle is thus needed to achieve acceptable on track performance while avoiding skew impact in neighboring tracks.
Existing processes for manufacturing PMR writer poles, however, generally produce a varying sidewall angle from the pole's yoke to its air-bearing surface (ABS). FIG. 1 illustrates this variation for four PMR writer main poles manufactured using existing processes. The sidewall angle continuously increases from the ABS through the yoke region. This sidewall angle increase from the ABS to the yoke results in an increase in on track reverse overwrite loss without any corresponding benefit to skew impact.
For example, existing Alumina (Al2O3) based damascene reactive ion etching (“RIE”) processes produce an inconsistent sidewall angle from the ABS 120 through the yoke region 110 due to the RIE loading effect. Under the RIE loading effect, the yoke region etches at a faster rate than the ABS region (assuming the same etching chemistry and selectivity in both regions) because the yoke region has a larger surface area. The faster etching process in the yoke region results in a larger sidewall angle in the yoke region in contrast to the ABS region.